Eleonora Cremonini

Systemic Oxidative Stress in Older Patients with Mild Cognitive Impairment or Late Onset Alzheimer's Disease.

A large body of evidences obtained in human and animal brain tissue suggest a role of oxidative stress (OxS) in the pathogenesis of late onset Alzheimers disease (LOAD); on the contrary, data on peripheral markers of OxS in LOAD are still controversial. We evaluated the serum levels of products of lipid peroxidation, hydroperoxides, advanced oxidation protein products, total and residual antioxidant power, thiols, and uric acid in a sample of 334 older individuals: 101 LOAD patients, 134 patients with mild cognitive impairment (MCI), and 99 controls. At univariate analysis, serum hydroperoxides were higher while residual antioxidant power was lower in MCI and LOAD compared with in controls. By multivariate logistic regression analysis we found that, compared with controls, high levels (over median value) of serum hydroperoxides were independently associated with an increase in the likehood of having MCI (Odd Ratio: 2.59, 95% Confidence Interval: 1.08-6.21) or LOAD (OR: 4.09, 95%CI: 1.36-11.81). Furthermore, low levels of residual antioxidant power (below the median value) were associated with increased risk of having MCI (OR: 3.97, 95% CI: 1.62-9.72), but not dementia (OR: 2.31, 95%CI: 0.83-6.63). Our study suggests that a systemic redox-imbalance leading to OxS might be associated not only with LOAD but also with MCI.

Hypoxia induces cell damage via oxidative stress in retinal epithelial cells

Abstract Retinal diseases (RD), including diabetic retinopathy, are among the most important eye diseases in industrialized countries. RD is characterized by abnormal angiogenesis associated with an increase in cell proliferation and apoptosis. Hypoxia could be one of the triggers of the pathogenic mechanism of this disease. A key regulatory component of the cells hypoxia response system is hypoxia-inducible factor 1 alpha (HIF-1α). It has been demonstrated that the induction of HIF-1α expression can be also achieved in vitro by exposure with cobalt chloride (CoCl2), leading to an intracellular hypoxia-like state. In this study we have investigated the effects of CoCl2 on human retinal epithelium cells (hRPE), which are an integral part of the blood–retinal barrier, with the aim to determine the possible role of oxidative stress in chemical hypoxia-induced damage in retinal epithelial cells. Our data showed that CoCl2 treatment is able to induce HIF-1α expression, that parallels with the formation of reactive oxygen species (ROS) and the increase of lipid 8-isoprostanes and 4-hydroxynonenal (4-HNE) protein adducts levels. In addition we observed the activation of the redox-sensitive transcription factor nuclear factor-kappaB (NFkB) by CoCl2 which can explain the increased levels of vascular endothelial growth factor (VEGF). The increased number of dead cells seems to be related to an apoptotic process. Taken together these evidences suggest that oxidative stress induced by hypoxia might be involved in RD development through the stimulation of two key-events of RD such as neo-angiogenesis and apoptosis.

Oxidative Stress and Bone Resorption Interplay as a Possible Trigger for Postmenopausal Osteoporosis

The underlying mechanism in postmenopausal osteoporosis (PO) is an imbalance between bone resorption and formation. This study was conducted to investigate whether oxidative stress (OxS) might have a role in this derangement of bone homeostasis. In a sample of 167 postmenopausal women, we found that increased serum levels of a lipid peroxidation marker, hydroperoxides, were negatively and independently associated with decreased bone mineral density (BMD) in total body (r = −0.192, P < 0.05), lumbar spine (r = −0.282, P < 0.01), and total hip (r = −0.282, P < 0.05), as well as with increased bone resorption rate (r = 0.233, P < 0.05), as assessed by the serum concentration of C-terminal telopeptide of type I collagen (CTX-1). On the contrary, the OxS marker failed to be correlated with the serum levels of bone-specific alkaline phosphatase (BAP), that is, elective marker of bone formation. Importantly, multiple regression analysis revealed that hydroperoxides is a determinant factor for the statistical association between lumbar spine BMD and CTX-1 levels. Taken together, our data suggest that OxS might mediate, by enhancing bone resorption, the uncoupling of bone turnover that underlies PO development.

Systemic Oxidative Stress and Conversion to Dementia of Elderly Patients with Mild Cognitive Impairment

Mild cognitive impairment (MCI) is regarded as a prodromal phase of late onset Alzheimers disease (LOAD). It has been proposed that oxidative stress (OxS) might be implicated in the pathogenesis of LOAD. The aim of this study was to investigate whether a redox imbalance measured as serum level of hydroperoxides (i.e., by-products of lipid peroxidation) and/or serum antioxidant capacity might be predictive of the clinical progression of MCI to LOAD. The levels of these two markers were measured in 111 patients with MCI (follow-up: 2.0 ± 0.6 years), 105 patients with LOAD, and 118 nondemented healthy controls. Multivariate analysis adjusted for potential confounding factors, including age, gender, smoking, and comorbidities, showed a significant increase (P < 0.05) in baseline levels of OxS in MCI and LOAD as compared to cognitive healthy controls. No differences in either of OxS markers were found by comparing MCI patients who converted (n = 29) or not converted (n = 82) to LOAD. Overall, these results suggest that systemic OxS might be a precocious feature of MCI and LOAD. However, the role of OxS as an early prognostic marker of progression to LOAD needs further investigations.

(-)-Epicatechin improves insulin sensitivity in high fat diet-fed mice.

Obesity constitutes a major public health concern, being frequently associated with type 2 diabetes (T2D). Evidence from studies in humans and experimental animals suggest that consumption of the flavan-3-ol (-)-epicatechin (EC) and of EC-rich foods may improve insulin sensitivity. To further understand the potential benefits of dietary EC consumption on insulin resistance, this study investigated the capacity of EC supplementation to prevent high fat diet (HFD)-induced insulin resistance in mice. To assess the underlying mechanisms, the effects of HFD and EC consumption on the activation of the insulin cascade and of its negative modulators were evaluated. HFD consumption for 15 w caused obesity and insulin resistance in C57BL/6J mice as evidenced by high fasted and fed plasma glucose and insulin levels, and impaired ITT and GTT tests. This was associated with alterations in the activation of components of the insulin-triggered signaling cascade (insulin receptor, IRS1, ERK1/2, Akt) in adipose and liver tissues. EC supplementation prevented/ameliorated all these parameters. EC acted improving insulin sensitivity in the HFD-fed mice in part through a downregulation of the inhibitory molecules JNK, IKK, PKC and protein tyrosine phosphatase 1B (PTP1B). Thus, the above results suggest that consumption of EC-rich foods could constitute a dietary strategy to mitigate obesity-associated insulin resistance.

(-)-Epicatechin in the prevention of tumor necrosis alpha-induced loss of Caco-2 cell barrier integrity.

An increased permeability of the intestinal barrier is proposed as a major event in the pathophysiology of inflammatory bowel diseases (IBD). Tumor necrosis alpha (TNFα) plays a central role in IBD pathogenesis, in part promoting tight function (TJ) barrier dysfunction. Food extracts enriched in (-)-epicatechin (EC) prevent the development or improve the progression of IBD in animal models. This study investigated the capacity of EC to inhibit TNFα-induced permeabilization of Caco-2 cell monolayers, characterizing the underlying mechanisms. Caco-2 cells differentiated into intestinal epithelial cells were incubated in the absence/presence of TNFα, with or without the addition of 0.5-5 μM EC. TNFα triggered cell monolayer permeabilization, decreasing transepithelial electrical resistance (TEER) and increasing the paracellular transport of fluorescein sulfonic acid. The permeabilizing effects of TNFα were not due to Caco-2 cell apoptosis as evaluated by DNA fragmentation, caspase 3 and 9 activation, and cell morphology. EC prevented TNFα-triggered Caco-2 monolayer permeabilization and acted inhibiting the associated: (i) NADPH oxidase (NOX)-mediated increased oxidant production, (ii) NF-κB (IκBα phosphorylation, p50 and RelA nuclear transport, and nuclear NF-κB-DNA binding) and ERK1/2 activation, (iii) increased myosin light kinase expression, and decreased TJ protein ZO-1 levels. In summary, EC prevented TNFα-mediated Caco-2 cell barrier permeabilization in part through the inhibition of NOX/NF-κB activation and downstream TJ disruption. Diets rich in EC could contribute to ameliorate IBD-associated increased intestinal permeability.

17β-estradiol levels and oxidative balance in a population of pre-, peri-, and post-menopausal women

Background. The high incidence of various diseases observed in post-menopausal women has been widely associated to the decline of 17β-estradiol (E2) occurring in correspondence of menopausal transition. One of the mechanisms suggested to explain this link takes into account the ability of E2 to counteract oxidative stress (OS) which is believed to play an important role in several pathogenic processes. Aim. To investigate whether stages of womens life characterized by different levels of E2 influence OS. Subjects and methods. We conducted a cross sectional study of OS markers in 159 women subdivided in 65 pre-menopausal, 36 peri-menopausal, and 58 post-menopausal classified according to the Staging of Reproductive Aging Workshop (STRAW) criteria. E2, follicle-stimulating hormone, and markers of OS including hydroperoxides, thiols, uric acid, total and residual antioxidant power, were assessed. Results. After adjustment for covariates, only total antioxidant power was significantly different according to menopausal status (p <0.01), with lower value in pre- with respect peri- and post-menopausal women. No significant correlations between E2 levels and OS markers were detected. Conclusions. Endogen E2, and, consequently, its decline during menopausal transition, is not a determinant factor for OS.

Anti-inflammatory actions of (−)-epicatechin in the adipose tissue of obese mice

Obesity and type 2 diabetes (T2D) are major public health concerns. Visceral adipose tissue inflammation is considered a significant contributor to obesity-associated T2D development. We previously showed that the flavan-3-ol (-)-epicatechin (EC) can mitigate insulin resistance in mice fed a high fat diet (HFD). This study investigated the capacity of EC to inhibit visceral adipose tissue inflammation occurring as a consequence of HFD consumption in C57BL/6J mice, and characterized the underlying mechanisms. In association with the development of obesity and insulin resistance, HFD consumption caused inflammation in the visceral adipose tissue as evidenced by activation of the pro-inflammatory transcription factor NF-κB and increased tissue levels of the macrophage marker F4/80, tumor necrosis factor alpha (TNFα), and the chemokine MCP-1. EC supplementation mitigated all these events. In addition, we observed activation of the three branches of the unfolded protein response (UPR), and upregulation of NADPH oxidases NOX4 and NOX2 in visceral fat of mice fed HFD. These can account, at least in part, for the associated oxidative stress and activation of the redox sensitive NF-κB. Notably, EC supplementation mitigated this and the release of pro-inflammatory proteins from metabolically stressed adipocytes. Attenuation of adipocyte endoplasmic reticulum (ER) and oxidative stress by EC could contribute to decreased inflammation and improved visceral adipose tissue insulin sensitivity. Our results support the concept that consumption of EC-rich foods could mitigate obesity-associated insulin resistance through attenuation of adipose tissue inflammation.

Metabolic transitions at menopause: In post-menopausal women the increase in serum uric acid correlates with abdominal adiposity as assessed by DXA

OBJECTIVES The present study aimed to investigate any associations between parameters of body fat mass distribution and levels of serum uric acid (sUA), a well-documented cardiovascular risk factor, among non-obese women ranging from pre- to post-menopausal status. METHODS In this cross-sectional population-based study we assessed body fat distribution by dual-energy-X-ray absorptiometry (DXA), and sUA levels in 101 pre- and 134 post-menopausal non-obese apparently healthy women. RESULTS Multivariate stepwise regression analysis revealed that sUA was independently associated to the indicators of overall fatness, i.e. body mass index (β=0.339, p<0.001) and DXA-assessed total and percentage body fat (β=0.366, p<0.001 and β=0.412, p<0.001, respectively), only among post-menopausal women. Within this sample subset, trunk (i.e. central) fat mass emerged as a strong predictor of sUA (β=0.408, p<0.001), after taking the potential confounders (including body mass index) into account. CONCLUSION Central fat accumulation was found to be independently associated with higher sUA levels among non-obese women in post- but not among those in pre-menopause.

The PI3K/Akt pathway is involved in procyanidin‐mediated suppression of human colorectal cancer cell growth

Colorectal cancer (CRC) has the third highest incidence worldwide. Epidemiological studies showed that the consumption of fruit and vegetables containing procyanidins (PCA), polymers of flavan‐3‐ols, is associated with lower CRC risk. However, the molecular mechanisms supporting this positive association are unclear. This study investigated the capacity of PCA with different degrees of polymerization to reduce CRC cell growth, characterizing the underlying mechanisms. Compared to the monomer ((−)‐epicatechin) and the trimer, the hexamer (Hex) was the most active at reducing CRC cell viability. Hex caused a concentration‐ (2.5–50 μM) and time‐ (24–72 h) dependent decrease in the viability of six human CRC cell lines in culture. Hex caused CRC apoptotic Caco‐2 cell death within 24 h, as evidenced by caspase 3 and caspase 9 activation, DNA fragmentation, and changes in nuclear morphology/staining. Hex‐induced apoptosis occurs through the mitochondrial pathway, as evidenced by an increased Bad mitochondrial translocation, and cytochrome c release from the mitochondria to the cytosol. Hex also arrested the Caco‐2 cell cycle at G2/M phase and upregulated genes involved in autophagy. Mechanistically, in Caco‐2 cells Hex inhibited the PI3K/Akt signaling pathway, causing the downstream downregulation of proteins involved in the regulation of cell survival (Bad, GSK‐3β). Accordingly, the Akt inhibitor MKK‐2206 decreased Bad and GSK‐3β phosphorylation. MKK‐2206 decreased cell growth, having an additive effect with Hex. In conclusion, our results show that large PCA can inhibit CRC cell growth via the Akt kinase pathway, demonstrating a mechanism to explain the epidemiological evidence linking PCA‐rich diets with lower CRC risk.